The present invention relates to an image forming apparatus for obtaining image in an electrophotographic way for use as a printer, a copying machine, a facsimile machine, or similar machines.
There have been many prior disclosures about the electrophotographic way to reproduce color images. In the Japanese Patent Application Laid-Open No. 61-100770, for example, a photoreceptor drum of image carrier has a latent image formed and developed corresponding to number of decomposed colors of an original picture. The image is transferred to a transfer drum every time it is developed to form multi-color image on the transfer drum. After this, it is transferred onto recording paper to obtain color copy. However, the apparatus of the method described has the disadvantage that it is needed to have a transfer drum which is large enough to be able to whole page of image on a surface thereof in addition on the photoreceptor drum. The apparatus is unavoidably made to a large size and complicated in the construction.
As another example, in the apparatus disclosed in the Japanese Patent Application Laid-Open No. 61-149972, a photoreceptor drum has a latent image formed and developed corresponding to number decomposed colors of an original picture. The image is transferred to transfer material every time development to reproduce multi-color copy. However, the apparatus described above have the disadvantage that it is hard to accurately register a plurality of color images to obtain quality color copy.
As another example of the conventional apparatuses, registration of color toner images are registered on a photoreceptor drum by repeating forming of latent images corresponding to number of decomposed colors of an original picture on the photoreceptor drum and developing them with color toners. After this, the registered image is transferred to obtain a color image. This basic process for forming multi-color image is disclosed in, for example, the Japanese Patent Application Laid-Open Nos. 60-75850, 60-76766, 60-95456, 60-95458, and 60-158475.
In the multi-color image forming apparatus in which the images are registered to obtain the color image, there are provided around the photoreceptor drum a plurality of developing sections containing toners of different colors. The photoreceptor drum is ordinarily turned a plurality of times to develop the latent images on the photoreceptor drum to reproduce the color image.
On the other hand, for analog copying machines of monochrome and color type using an electrophotographic method and image forming apparatuses, such as copying machine and printer, using a semiconductor laser or LED scanning system, it has been proposed to assemble parts of the image forming arrangements in a cartridge for replacing or supplying consumable photoreceptors, developing carrier, cleaning members, and developing toner. The cartridge containing the major image forming arrangements can be taken out of the apparatus body for maintenance or replacement. There also have been proposed many constructions that the feed path for the transfer material having image formed by the image forming arrangements can be made to open for easy removal of the transfer material upon jamming.
As a typical example of the constructions mentioned above, the Japanese Patent Publication No. 58-54392 proposes that a photoreceptor drum, a developing arrangement, and a cleaner are together mounted on a supporting member. They can be pulled out of the apparatus body for easy maintenance and replacement.
The Japanese Patent Application Laid-Open No. 57-154255 has proposed that a cartridge having major image forming arrangements integrated together is disposable. The Japanese Patent Application Laid-Open No. 59-147366, which also uses a similar disposable cartridge, has disclosed a printer in which a semiconductor laser is used to make exposure, scanning, and writing of dots to form latent image on a photoreceptor drum.
Also, these laid-opens have disclosed that an upper casing of a dividable structure can be opened to make the transfer material feed path clear for taking the transfer material out upon jamming. The Laid-Open No. 57-154255 has a disposable process cartridge provided on an upper casing of a two-dividable structure so that it can be replaced for good workability of the cartridge and easy clearing of jamming.
The Japanese Patent Application Laid-Open No. 58-1161 has disclosed a two-dividable structure in chief view of easy replacement of process cartridges including a supply toner cartridge and a cleaning cartridge for collected toner. In particular, the process cartridges are provided on a lower casing for high maintainability.
The Japanese Patent Application Laid-Open Nos. 63-244058, 63-244059, 63-244064, and 1-179168 have proposed that the above mentioned structures are made vertical. These aim at unidirectional manipulations and easy clearing of jamming.
However, there has not been proposed a compact printer having a replaceable process cartridge comprising a developing arrangement and an image carrier which can be easily loaded in or taken out of the apparatus body, and is free of uneasy leakage and spilling of toner or developing agent from the developing arrangement upon insertion in or removal from the apparatus body or upon clearing the transfer material of jamming.
The Japanese Patent Application Laid-Open No. 58-190961 has proposed a printer of two-dividable structure that a process cartridge provided on an upper casing can be always kept horizontal not to spill waste toner when it is opened. Although loading of the cartridge and clearing of jamming can be made easily, it does not solve such problems as leakage and spilling of the toner upon loading the cartridge, clearing of jamming, and maintenance and replacement of them.
There have been other disclosures in the Japanese Patent Application Laid-Open No. 58-72159 in which a disposable cartridge is provided on an upper casing of the two-dividable structure mentioned above for easy clearing of jamming and in the Japanese Patent Application Laid-Open No. 58-1161 in which a process cartridge having a developing, cleaning, and photoreceptor arrangements is provided on a lower casing for easy supply and replacement of collected toner, and is brought upward upon clearing of jamming. In these prior arts, workability in replacement of the process cartridge contradicts easiness in clearing of jamming. Each of these process cartridges has the developing section and the cleaning section on its bottom. These sections face a transfer electrode with a sheet feed path put therebetween. The toner spills out of the developing arrangement and the cleaning arrangement upon replacement of the process cartridge or by external vibration or impacts to the apparatus body even if the cartridge is strictly sealed. This causes contamination in the apparatus and to the transfer paper.
The Japanese Utility Model Application Laid-Open No. 63-194357 has disclosed a printer having a process cartridge built in it and having a flat sheet feed path formed on its upper portion. However, it is limited in the sheet feed path from a transfer material separation section of a photoreceptor drum to a fixing section, or it does not solve a problem in the sheet feed section. The printer also is disadvantageous in that it is hard to clear jams upon division of the apparatus into two, is not compact as a whole due to a stack sheet feed construction of up-stand type, and has a limited opening of an upper casing upon division into two. That is, the printer is not always convenient for users.
In turn, there have been proposed many color image forming bodies, for example, by the present applicant in the Japanese Patent Application Laid-Open No. 64-192874. They, as described previously, includes a photoreceptor drum having a photoconductive substance coated or evaporated on surface of a drum and a belt-like image forming body having the photoconductive substance coated on or applied to a flexible belt. The belt-like image forming body (hereinafter also referred to as the photoreceptor belt) is determined in shape by putting it between revolving rollers including a drive roller. This is effective for making the color image forming apparatus compact with effective use of space. Also, it is desirable in that the photoreceptor belt can be run along with a small curvature so that the transfer material can be separated by making use of the curvature with use of a revolving roller of small diameter. This prevents the transfer material from being not separated.
In the color image forming apparatus using such a photoreceptor belt, image forming arrangements, including a charging arrangement, an image exposure arrangement, a plurality of developing sections, and a cleaning arrangement, are provided to face an outside surface of the photoreceptor belt, particularly a lower part of the outside surface. The image forming arrangements are assembled in a process cartridge together with the photoreceptor belt as an independent unit so that the cartridge can be loaded into or taken out of the apparatus body as necessary.
The transfer material having the color toner image transferred onto it can be discharged onto a discharge tray provided on a top of the apparatus with its copied side down. This makes the apparatus installation area narrower.
Recently, the Japanese Patent Application Laid-Open Nos. 64-40850 and 63-244059 mentioned above have proposed use of a compact cartridge to solve such problems as sheet feed, clearing of jamming. They also make unidirectional manipulation possible.
The Japanese Patent Application Laid-Open No. 63-85763 has disclosed a control concept for indications upon consumption of the toner in the process cartridge and the end of service life of the photoreceptor.
However, there have not been proposed a compact, easy-to-use image forming apparatus yet which meets all the conditions that jamming can be easily cleared, the toner cannot be spilled upon operation and manipulation of the cartridge, it can be easily replaced, and any of the manipulations can be made on the front of the apparatus unidirectionally.
Also, the Japanese Patent Application Laid-Open No. 61-279870 has proposed another image forming apparatus in which consumption articles and materials can be easily handled and treated and limitation of working space can be minimized by making a loading direction of a transfer material coincide with a loading and unloading direction of a process cartridge provided on an upper casing.
However, the apparatus mentioned in the Japanese Patent Application Laid-Open No. 61-279870 have the disadvantage that the operator himself has to move the movable sections to clear the sheet feed route of the transfer material, thereby making the working room. This is troublesome work. The working room obtained for clearing of jamming is too narrow to easily insert a hand into it to remove the jamming paper. To release the sheet feed route, he or she had to search for a position where the jamming paper is. If the sheet feed route is complicated, he or she had to move a plurality of movable portions at a time to release a plurality of sheet feed routes. He or she was not only confused in shooting the jamming position for a long time, but also might be involved in erroneous manipulations, resulting in some troubles.
The conventional image forming apparatuses have the disadvantage in the workability that as they were ordinarily leveled at around a waste of the operator, he or she had to sit down on his or her kneels or bend his or her body not only to see, but also to clear of the jamming paper.
In any way, as the conventional apparatuses caused the operator himself or herself to move the movable sections to release the sheet feed route, they were not only disadvantageous in the workability, but also might injure him or her or the image carrier if his or her hand had to force or put into narrow spaces.
In order to replace the process cartridge or cassette of the conventional apparatuses, the operator had to pull it out of the apparatus body to a great extent. This work was not only very troublesome, but also needed for him or her to have a mighty force to bring up the heavy process cartridge or cassette which might be in contact with the sheet feed roller or to erroneously drop it down.
In short, the conventional apparatuses are disadvantageous in the simplicity of work and safety when the jamming paper is to be removed or the process cartridge or cassette has to be replaced.